Quantitatively increased somatic transposition of transposable elements in Drosophila strains compromised for RNAi.

In Drosophila melanogaster, small RNAs homologous to transposable elements (TEs) are of two types: piRNA (piwi-interacting RNA) with size 23-29nt and siRNA (small interfering RNA) with size 19-22nt. The siRNA pathway is suggested to silence TE activities in somatic tissues based on TE expression profiles, but direct evidence of transposition is lacking. Here we developed an efficient FISH (fluorescence in Situ hybridization) based method for polytene chromosomes from larval salivary glands to reveal new TE insertions.

Identification of Inverse Regulator-a (Inr-a) as Synonymous with Pre-mRNA Cleavage Complex II Protein (Pcf11) in Drosophila.

A common modulation of gene expression in aneuploids is an inverse correlation of the monitored gene with the dosage of another segment of the genome. Such effects can be reduced to the action of single genes. One gene previously found to modulate leaky alleles of the white eye color gene in Drosophila is Inverse regulator-a (Inr-a).

Re-evaluation of the function of the male specific lethal complex in Drosophila.

A set of proteins and noncoding RNAs, referred to as the male specific lethal (MSL) complex, is present on the male X chromosome in Drosophila and has been postulated to be responsible for dosage compensation of this chromosome - the up-regulation of its expression to be equal to that of two X chromosomes in females. This hypothesis is evaluated in view of lesser known aspects of dosage compensation such as the fact that metafemales with three X chromosomes also have equal expression to normal females, which would require a down-regulation of each gene copy. Moreover, when this complex is ectopically expressed in females or specifically targeted to a reporter in males, there is no increase in expression of the genes or targets with which it is associated.

Reflections on the inhibition of RNAi by cell death signaling.

Mutations and most transgenes that induce ectopic cell death in Drosophila will produce an inhibitory effect on RNA interference (RNAi) in adjacent cells. When extensive cell death is sporadically induced using a heat shock promoted-head involution defective (hs-hid) transgene, molecular attributes of this inhibition can be studied. For a Green Fluorescent Protein (GFP) RNAi construct, cell death causes a greater accumulation of the mature mRNA and the double stranded RNA with an accompanying reduction in the homologous siRNAs.

Inhibition of RNA interference and modulation of transposable element expression by cell death in Drosophila.

RNA interference (RNAi) regulates gene expression by sequence-specific destruction of RNA. It acts as a defense mechanism against viruses and represses the expression of transposable elements (TEs) and some endogenous genes. We report that mutations and transgene constructs that condition cell death suppress RNA interference in adjacent cells in Drosophila melanogaster.

Genetics and biochemistry of RNAi in Drosophila.

RNA interference (RNAi) is the technique employing double-stranded RNA to target the destruction of homologous messenger RNAs. It has gained wide usage in genetics. While having the potential for many practical applications, it is a reflection of a much broader spectrum of small RNA-mediated processes in the cell.

Phosphorylation regulates integration of the yeast Ty5 retrotransposon into heterochromatin.

The yeast Ty5 retrotransposon preferentially integrates into heterochromatin at the telomeres and silent mating loci. Target specificity is mediated by a small domain of Ty5 integrase (the targeting domain, TD), which interacts with the heterochromatin protein Sir4 and tethers the integration complex to target sites. Here we demonstrate that TD is phosphorylated and that phosphorylation is required for interaction with Sir4.

Polycomb, pairing and PIWI--RNA silencing and nuclear interactions.

In Drosophila, the RNA interference (RNAi) genes participate in Polycomb (Pc)-mediated transgene silencing. Recently, the involvement of the RNAi genes in Pc silencing, pairing-sensitive silencing and long-range contacts among Pc-associated sequences has been explored. These Pc-associated sequences are involved with the control of the proper expression of developmental HOX genes.

Global analysis of siRNA-mediated transcriptional gene silencing.

The RNAi machinery is not only involved with post-transcriptional degradation of messenger RNAs, but also used for targeting of chromatin changes associated with transcriptional silencing. Two recent papers determine the global patterns of gene expression and chromatin modifications produced by the RNAi machinery in fission yeast.(9, 10) The major sites include the outer centromere repeats, the mating-type locus and subtelomeric regions.

RNA silencing in Drosophila.

Knowledge of the role of RNA in affecting gene expression has expanded in the past several years. Small RNAs serve as homology guides to target messenger RNAs for destruction at the post-transcriptional level in the experimental technique known as RNA interference and in the silencing of some transgenes. These small RNAs are also involved in sequence-specific targeting of chromatin modifications for transcriptional silencing of transgenes, transposable elements, heterochromatin and some cases of Polycomb-mediated gene silencing.